So far there has been known subcutaneous implantation by which one or more solid preparations are administered to the body of a patient to perform medical treatments. In the implantation, however, it is required to perform a surgical operation accompanied with physical and mental sufferings of the patient, thus making it difficult to frequently perform subcutaneous implantation of solid preparations.
To solve such a problem, some of the inventors have proposed use of an instrument for administering solid preparations under the skin, for example, in EP-A-139286, Japanese patent applications laid-open Nos. 61-79470, and 61-82761. The instrument generally comprises a fine tube and a plunger removably mounted therein and is operated in the following manner. Firstly, the plunger is pulled out of the fine tube and, after loading a solid preparation into the fine tube from its rear end, the plunger is inserted again into the fine tube. The solid preparation is then injected into the body by inserting the fine tube into the body and then pushing the plunger.
Such an instrument makes it possible to implant solid preparations under the skin of the body without performing surgical operations, but it has various problems awaiting a solution. For example, the operations are troublesome and take a long time since the plunger must be removed from the fine tube each time when loading the solid preparation into the fine tube. Since the solid preparation is frequently caught by a joint of the fine tube, it is difficult to administer the solid preparations smoothly, thus making it impossible to administer two or more preparations at the same time. Further, the plunger is an elongated fine member, so that the insertion of the plunger into the needle is difficult and requires prudent cares to prevent the plunger from bending or breaking. The longer the fine tube, the greater the force required for the sliding movement of the plunger. In addition, there is a fear that the solid preparation would lose its original form by the friction with the inside wall of the fine tube during movement from the rear end of the fine tube to the front end. The instrument is designed to administer a completely or partially bared solid preparation to the body, thus making it difficult to aseptically handle the solid preparations to be loaded into the instrument.